Swim stress did not induce phosphorylation of MKK3/6. Note the absence of a band for P-MKK3/6 at ~40 kD, either in control or swim stressed hippocampal lysates, whereas an induced band is visible in the positive control cell extracts. Also note the unknown ~37 and 48 kD proteins induced by swim stress. Other brain regions examined exhibited a similar pattern. 3T3, lysates of NIH/3T3 cells treated with (+) or without (-) UV radiation (40 mJ, 45 minutes recovery time); C6, lysates of C6 glioma cells treated with (+) or without (-) anisomycin (25 μg/ml, 30 min); MW, molecular weight markers.